Refractory hypertension and obstructive sleep apnea.

Refractory hypertension (RfH) is the most difficult-to-control form of hypertension and carries the highest cardiovascular risk. It is estimated to account for 0.5-1% of all forms of hypertension. Sleep apnea syndrome (OSA), defined as the repeated partial or complete interruption of the airway flow during sleep, is highly prevalent, with almost one billion people worldwide suffering from it. Both diseases share a pathophysiological mechanism: the hyperactivation of the sympathetic nervous system. In recent years, a clinical relationship between RfH and OSA has been demonstrated. 80-90% of patients with RfH suffer from OSA, which could partly explain the refractoriness to treatment. Treatment of OSA with continuous positive airway pressure (CPAP) significantly reduces blood pressure by 8-10 mmHg in patients with RfH.